1. Field of the Invention
The present invention relates to an image processing apparatus and image processing method for image processing an image such that a printout apparatus prints out the image corresponding to image data generated by various applications. More particularly, the invention relates to an image processing apparatus and method for image processing image data for printing, such that a printout apparatus prints the image data using a printing plate.
2. Description of the Related Art
As digitization in the field of a printing process, DTP (Desktop Publishing) is penetrating. In the DTP, a page layout is generated by generating, processing and/or editing an image by using various applications on a processing device such as a personal computer or workstation. A film used for exposing a printing plate is generated on the basis of the page layout (image setter or RIP for plate), or a printing plate is generated by writing data directly to a printing plate (CTP: Computer to Plate).
In the operation, an image of a page layout is separated into colors of C, M, Y, and K and a printing plate is exposed on the basis of image data of each color, thereby generating a press plate obtained by forming a halftone image on the printing plate. Ink of a predetermined color is applied to the press plate of each color, and overlapping printing is performed, thereby forming a color image on a printing matter.
When a plate misalignment occurs in the printing process using a press plate, there are cases that color shift occurs in a border or the like of an image. To prevent deterioration in quality caused by the plate misalignment, overprinting and trapping process is performed. In the printing process using press plates, to overprint images of color components, the overprinting and trapping process is performed, thereby enabling an image to be properly reproduced.
In practice, prior to printing using press plates, a proof is made. A page layout is displayed on a monitor or an image is printed by a printout apparatus such as a laser printer or page printer by using the WYSIWYG function.
At the time of checking the overprinting and trapping process by using a printout apparatus, an image drawing command of performing a color separating process for generating images of color components of C, M, Y, and K like has to be executed by an image processing apparatus having a special function.
In the case of performing color separation output, however, pages of the number of plates have to be transferred, so that the data size becomes at least four times as large as that of normal composite output. When a spot color is included, there is the possibility that the data size further increases. Consequently, data transfer time and processing time become longer.
On the other hand, various efficient methods used when a trouble occurs in color separation output have been proposed (refer to, for example, Japanese Patent Application Laid-open (JP-A) Nos. 2002-292817, 2002-297360, and 2002-300414).
Those proposals however are not related to a method of easily improving transfer time and processing time.
The occasions of using PDF are increasing. However, special software for performing color separation output for the PDF is necessary. To check overprint or trapping in color separation output, a work which is complicated a little is required.
At the time of conducting proof by using a printer, there are cases such that overprint or trapping is reproduced in a composite output using an image drawing command of performing normal color printing without executing a color separation process.
In this case, by using a technique called “In-RIP separation” of performing color separation process for an image drawing command corresponding to a composite output on the side of the RIP (printer), an image subjected to the overprinting and trapping process can be reproduced. Hitherto, overprinting and trapping is reproduced in a composite output by using such a technique.
In the field of printing, in addition to the colors of C, M, Y, and K, there is a case that a so-called spot color different from the C, M, Y, and K colors is used. Although an image of a spot color can be reproduced by the In-RIP separation, a spot color has to be set prior to image processing for printing.
For a composite output, however, a process of setting a spot color prior to the image processing is not included. Consequently, even if In-RIP separation is used and a spot color is designated for an image (object) the image is processed as an object expressed in CMYK, so that overprint of the spot color cannot be reproduced accurately.
Therefore, for example, as shown in FIG. 8, when an object 90 of CMYK of C=80%, M=0%, Y=0%, and K=20% and an object 92 of a spot color of C=10%, M=100%, Y=50%, and K=0% are overlapped in an overprint setting, to simulate a printed matter using press plates, in an overprint portion 94, C=90%, M=100%, Y=50%, and K=20%, so that an adding process has to be performed for the color C.
On a printed matter obtained by using a printer, the spot color cannot be reproduced properly, so that the color C is knocked out, resulting C=10%, M=100%, Y=50%, and K=20%. That is, even when a spot color is set in a composite output, the spot color name cannot be known prior to the image processing, so that it is difficult to separate an image into the spot color.
As described above, even when In-RIP separation is used, if a spot color is designated, an image is processed as an image (object) expressed in CMYK and it causes a problem such that an overprint of an object of a spot color cannot be accurately reproduced.